Adrian's communications business began as a one- person operation, but Adrian soon found that he had more work than he could do himself. Although it was not in his plan to hire any subcontractors during the first year, he decided to go ahead and bring in three contractors to work on new projects. At the same time, he decided to increase the contractor's daily fee to $500. In the market for sub-contractors, what is this an example of? a) positive supply shift b) negative demand shift c) negative supply shift d) positive demand shift